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PreprintCC BY 4.0arXiv

Achieving the Quantum Limits with Twin-Field Sensors

  • Yaohua Li
  • Fan Yang
  • Klaus Mølmer
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Abstract

Continuous measurements play a fundamental role in quantum experiments, yet understanding and extracting the maximal possible information in a continuous probe signal remains a significant challenge. In this work, we show that for a wide class of sensors, the quantum Fisher information bound can be saturated through a combined measurement of signals from the original sensor and a suitable system copy. We elucidate the physical mechanism of such a twin-field sensor (TFS) and study its performance across diverse implementations, ranging from two-level atoms to a hybrid quantum Rabi model. In all of these cases, we find that simple photon counting or homodyne detection saturates the theoretical quantum limit. We further prove that the TFS achieves the quantum limits for the joint sensing of pairs of parameters as quantified by the quantum Fisher information matrix.

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Cite

BibTeXRIS
BibTeX
@misc{li2026achieving,
  title = {{Achieving the Quantum Limits with Twin-Field Sensors}},
  author = {Yaohua Li and Fan Yang and Klaus Mølmer},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.07517},
  eprint = {2609.07517},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.07517},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Achieving the Quantum Limits with Twin-Field Sensors
AU  - Yaohua Li
AU  - Fan Yang
AU  - Klaus Mølmer
PY  - 2026
DA  - 2026/09/07
PB  - arXiv
DO  - 10.48550/arxiv.2609.07517
UR  - https://arxiv.org/abs/2609.07517
AB  - Continuous measurements play a fundamental role in quantum experiments, yet understanding and extracting the maximal possible information in a continuous probe signal remains a significant challenge. In this work, we show that for a wide class of sensors, the quantum Fisher information bound can be saturated through a combined measurement of signals from the original sensor and a suitable system copy. We elucidate the physical mechanism of such a twin-field sensor (TFS) and study its performance across diverse implementations, ranging from two-level atoms to a hybrid quantum Rabi model. In all of these cases, we find that simple photon counting or homodyne detection saturates the theoretical quantum limit. We further prove that the TFS achieves the quantum limits for the joint sensing of pairs of parameters as quantified by the quantum Fisher information matrix.
ER  -